Ion mobility spectrometer

Abstract

Disclosed is an ion mobility spectrometer. The ion mobility spectrometer comprises a sample injector ( 14 ), a semipermeable membrane ( 15 ), an ionization region ( 16 ), a terminal electrode ( 18 ), an ion storage region, a drift region and a Faraday plate ( 22 ), which are arranged along a drift tube in turn, wherein one or more air inlets ( 29 ) connected with a needle valve ( 30 ) and a first filtering device ( 31 ) are arranged in one side near the semipermeable membrane ( 15 ) of the ionization region ( 16 ), there is at least one opening in the terminal electrode ( 18 ), whose diameter is smaller than the diameter of the air inlets ( 29 ), an air outlet ( 28 ) connected with an air extracting pump ( 27 ) is arranged near the terminal electrode ( 18 ) in the ionization region ( 16 ), the drift region is separated from the ionization region ( 16 ) by a micropore structure of the ion storage region, another air outlet ( 25 ) connected with another air extracting pump ( 26 ) is arranged at one side near the Faraday plate ( 22 ) of the terminal electrode ( 18 ).

What is claimed is: 
     
       1. An ion mobility spectrometer, having a sample injector, a semipermeable membrane, an ionization region and a terminal electrode, which are arranged along a drift tube in turn, comprising:
 an air inlet connected with a needle valve and a first filtering device for intaking air arranged on one side of the ionization region adjacent to the semipermeable membrane; 
 at least one opening provided in the terminal electrode, whose diameter is smaller than a diameter of the air inlet; 
 a first air outlet connected with an air extracting pump for extracting air and provided in the ionization region adjacent to the terminal electrode; and 
 an ion mobility spectrometer having two meshed metal sheets for clamping the semi-permeable membrane therebetween. 
 
     
     
       2. The ion mobility spectrometer of  claim 1 , further comprising a focusing electrode positioned near to one side of the ionization region, which focuses ions formed in the ionization region so that the ions pass through the opening in the terminal electrode. 
     
     
       3. The ion mobility spectrometer of  claim 2 , wherein the focusing electrode has an opening with a diameter larger than that of the opening of the terminal electrode. 
     
     
       4. The ion mobility spectrometer of  claim 2 , wherein the semipermeable membrane, the ionization region, the focusing electrode and a drift region are air-tight except for the openings. 
     
     
       5. The ion mobility spectrometer of  claim 1 , further comprising:
 a drift region arranged at one side of the terminal electrode in which the side is away from the sample injector; and 
 a Faraday plate arranged at an end of the drift region, 
 wherein an opening arranged at the Faraday plate is connected with a second filtering device. 
 
     
     
       6. The ion mobility spectrometer of  claim 1  or  5 , further comprising a second air outlet arranged at one side of the terminal electrode and in an ion storage region, wherein the second air outlet is connected with another air extracting pump. 
     
     
       7. An ion mobility spectrometer comprising a sample injector, a semipermeable membrane, an ionization region, a terminal electrode, an ion storage region, a drift region and a storage region, which are arranged along a drift tube, comprising:
 the drift region separated from the ionization region by a micropore structure of the ion storage region; 
 an opening arranged in the ionization region adjacent to the terminal electrode, the opening being connected with an air extracting pump for extracting air; and 
 another air outlet arranged at one side of the terminal electrode and in an ion storage region, the another air outlet is connected with another air extracting pump.